Laser-induced fluorescence measurements of product penetration within an ultracompact combustor

Combustion product propagation within an ultracompact combustor (UCC) is examined using hydroxyl (OH) imaging. The UCC employs a cavity stabilization mechanism, which results in reduced size and weight as compared with those of typical swirl-stabilized combustors. Hydrogen fuel is injected along the outside surface of a circumferential cavity, where it is mixed with air. Following primary combustion within this circumferential cavity, either combustion products or continuing reactions propagate into a main axial-flow cavity, where combustion is completed and products exit the combustor with the main-cavity air flow. Planar laser-induced fluorescence of hydroxyl is used to study the propagation of OH from the circumferential into the main flow cavity with respect to changes in the flow ratios between the cavities and in the equivalence ratio. OH serves as a marker for the location of intermediate combustion products and is typically found within and following the primary reaction region of a flame. Through probability density functions of the peakOHintensity locations, the combustion product impingement into the main cavity is determined to be insensitive to the equivalence ratio. Flow ratios, however, are shown to affect the impingement locations, where increased air flow ratios can reduce the required combustor size by isolating reaction products solely within the secondary cavity.